1. Field of the Invention
The present invention relates to an Internet telephone, a server apparatus, and an Internet telephone system that perform a telephone call via the Internet, and relates to a calling method via an Internet network.
2. Description of Related Art
A conventional network that is used by so-called Internet telephone has been configured as follows.
Taking an Internet telephone system using H.323 protocol as an example, a calling management server (known as gatekeeper) is provided within an Internet telephone network. This gatekeeper has functions to receive a destination phone number from each telephone, to convert the phone number into a corresponding IP address, and to return the telephone number back to the originating telephone.
When an operator inputs the desired telephone number, the telephone number is called to the gate keeper. When the telephone receives, from the gatekeeper, an IP address that corresponds to the telephone number, an originating telephone can access, based on the IP address, a destination telephone via the gatekeeper, or directly access the destination telephone without involving the gatekeeper. Accordingly, a telephone call becomes available via the Internet (see Related Art 1).
In addition, a router is normally involved between the gatekeeper and each telephone. A plurality of Internet telephones, configuring a group in a network, are connected to such a router. Telephones within the same group have IP addresses having a common network address. In a normal corporate office setting, telephones within the same department are configured as the same group in the network.
FIG. 28(a) illustrates a network configuration of a general Internet telephone system. In the network shown in FIG. 28(a), router A 2802 and router B 2803 are connected to call management server (server) 2801. Internet telephones A1-A4, configuring group (A), are connected to router A 2802, while Internet telephones B1-B4, configuring group (B) are connected to router B 2803.
FIGS. 28(b) and (c) illustrate management charts that register telephone numbers assigned to each Internet telephone and the corresponding IP addresses. FIGS. 28(b) and (c) respectively illustrate management charts of group (A) and group (B). In this example, telephone numbers are extension numbers used in a corporate office setting.
As shown in FIG. 28(b), telephone numbers 1001-1004 are respectively assigned to Internet telephones (terminals) A1-A4, and have IP addresses of (192. 168. 1. 1)-(192. 168. 1. 4). Network address (192. 168. 1) is commonly used for the above IP addresses of group (A) terminals.
As shown in FIG. 28(c), telephone numbers 2001-2004 are respectively assigned to Internet telephones (terminals) B1-B4, and have IP addresses of (192. 168. 2. 1)-(192. 168. 2. 4). Network address (192. 168. 2) is commonly used for the above IP addresses of group (B) terminals.
[Related Art 1]
Japanese Patent Laid Open Publication 2002-101198 (Pages 4-5, FIG. 1)
The above-described conventional art has the following shortcomings.
In a case where a call is placed to a telephone in a department, and the telephone is busy, the caller needs to hang up the phone and to dial a different number of a telephone adjacent to the busy telephone, if it is for an urgent matter. Therefore, such a calling operation has been very cumbersome to the caller.
The above network configuration is further described using the example of terminal A1 placing a call to terminal B1. FIG. 29 is a sequence diagram illustrating an operation of a conventional Internet telephone system.
As shown in FIG. 29, when terminal A1 places a call to terminal B1, the caller first inputs telephone number (2001) of terminal B1. Upon obtaining the telephone number, terminal A1 transmits, to server 2801, a request for the IP address of terminal B1. Then, server 2801 provides the IP address of terminal B1. Based on the obtained IP address, terminal A1 places a call to terminal B1.
In this example, terminal B1 is busy, thus the connection to terminal B1 is unsuccessful, and terminal A1 receives a busy tone. Upon confirming the busy tone, the caller hangs up the telephone, and inputs telephone number (2002) of terminal B2. In the same process as calling terminal B1, terminal B2 is called when terminal A1 obtains the IP address of terminal B2 from server 2801.
In this example, terminal B2 is also busy, thus the connection to terminal B2 is unsuccessful, and terminal A1 receives a busy tone. Upon confirming the busy tone, the caller hangs up the telephone, and inputs telephone number (2003) of an adjacent terminal B3. In the same process as calling terminal B1 and terminal B2, terminal B3 is called when terminal A1 obtains the IP address of terminal B3 from server 2801.
In this example, terminal B3 is not busy, thus the connection between terminal A1 and terminal B3 is successful. Then, a message to the operator of terminal B1 is delivered to the operator of terminal B3. As described above, when one terminal in a department is busy, the operator needs to dial a different number of an adjacent terminal.